Semester of Graduation

Summer 2026

Degree

Master of Science (MS)

Department

Plant Pathology and Crop Physiology

Document Type

Thesis

Abstract

Sheath blight (SB), caused by Rhizoctonia solani AG1- IA, is one of the most damaging diseases of rice worldwide. In the United States, chemical control remains the primary management strategy due to limited genetic resistance and the partial effectiveness of cultural practices. Since the early 1970s, fungicide efficacy trials have been conducted annually at the LSU AgCenter Rice Research Station as part of general management studies and collaborative research and development efforts with the private sector. Collectively, these trials represent a unique, long‑term body of data that remains mostly unpublished in peer-review journals or in an inaccessible format. This study synthesizes over five decades of these trials to provide a qualitative and quantitative assessment of fungicide research trends, performance, and economic return. Trials reported in annual station reports that included at least one measure of SB intensity were selected. Data on disease severity and incidence, grain yield, fungicide treatments, and trial metadata were compiled. When treatments were reported using experimental codes, active ingredients (AI) were identified using publicly available sources. The qualitative review focused on temporal trends in fungicide chemistry and modes of action, highlighting a shift from a diverse set of AIs tested in early trials to the predominance of fungicides from the QoI, DMI, and SDHI groups in more recent years. Fungicide programs evaluated in ten or more trials were summarized using mixed effects multivariate meta‑analysis. Yield response and SB control were estimated relative to untreated controls. Selected fungicide programs, particularly azoxystrobin‑based treatments applied at the boot stage, consistently provided the greatest disease suppression and yield response. Moderator analysis indicated that fungicide performance was influenced by the year and varietal susceptibility and more consistent performance observed in susceptible than very susceptible. Scenarios incorporating application cost and crop price were simulated to estimate the probability that a fungicide program would generate a positive economic return. Azoxystrobin‑based programs showed the highest probability of economic return across simulated scenarios, whereas some propiconazole-based programs showed lower probabilities under comparable conditions. This study provides a robust, long‑term assessment of fungicide performance and trends for SB management in Louisiana.

Date

7-30-2026

Committee Chair

Dalla Lana, Felipe

LSU Acknowledgement

1

LSU Accessibility Acknowledgment

1

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Available for download on Saturday, July 14, 2029

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